The invention relates to a tomograph for producing transverse layer images of a radiography subject, having several sources of radiation, arranged with their focuses mutually offset by angles of equal size, having a radiation measuring arrangement which consists of a number of radiation receivers equal to the number of radiation sources, which determine the radiation intensity behind the subject, having a drive device which drives a rotating frame for the radiation sources and the radiation receivers, and also having a measured value converter for transforming the signals supplied by the radiation receivers into a layer image, and in which the radiation receivers are also arranged opposite the radiation sources, displaced by angles of equal size.
A tomograph of this type is described in the German Offenlegungsschrift 26 14 083 (U.S. Pat. No. 4,150,293 issued Apr. 17, 1979). In this tomograph, a computer is provided which processes the output signals of the radiation receivers, which are produced at different projections while the rotating frame is rotating, so that the radiation attenuation coefficients of specific points of the irradiated layer are calculated from them and may then be reproduced in image form. The drive device in the known tomograph is constructed so that for a scan it rotates the rotating frame by an angle which is equal to the angle of offset of the radiation sources and the radiation receivers. When there are three x-ray tubes and three radiation receivers it is necessary accordingly to rotate the rotating frame by 120.degree.. Thus, compared with the instance where only one x-ray tube and one radiation receiver are provided the scanning time is shortened by a third.
With the known tomograph of the initially mentioned type it is only possible to scan a single layer of the radiography subject in each case. If several layers of the radiography subject are to be examined it is necessary to move the patient support longitudinally by one step after one layer has been scanned and to make another scan. As a result of alternate scanning and patient support displacement which is necessary when several layers are examined, the time taken to complete the examination of several layers is relatively long.